Method for regulating pressures on milling rolls



July 19, 1955 F. M. ATKINSON 2,713,460

METHOD FOR REGULATING PRESSURES 0N MILLING ROLLS Filed Feb. 28, 1952f/VVlW/Zz? 5m M. ATKINSON .JI'IZMIK United States Patent METHOD FORREGULATING PRESSURES ON MILLING ROLLS Fred M. Atkinson, Minneapolis,Minn assignor to Atkinson Milling Company, Minneapolis, Minn., acorporation of Minnesota Application February 28, 1952, Serial No.274,013

4 Claims. (Cl. 241-43) This invention relates to fiour milling. Moreparticularly, it relates to the regulation of pressure exerted upon thevarious pairs of flour milling rolls to obtain the most efficientmilling operation.

In the process of grinding and reducing wheat into flour sizedparticles, the setting of the grinding rolls with relation to each otheris of primary importance. It is highly important, in the milling offlour, that the resulting product be of uniform quality. Production ofuniform quality products depends upon uniform settings on each pair ofrolls, and in the past this has been only imperfectly accomplished byindividuals using their own senses of touch and sight upon inspection ofthe continuously ground stock.

In more recent years the individuals actively engaged in the milling ofwheat have supplemented their own judgment by sieving samples of thefreshly ground product to determine the amount of grinding accomplished.This has been done with sieves of various sizes, shaken mechanically fora controlled length of time. This process, known as extraction, becausethe flour is thereby extracted from the coarser material, determines thepercentages of the diflerently sized particles in the ground stock. Itis a process which is both tedious and timeconsuming.

Experiments have been conducted by many people who have attempted toregulate the proper degree of grinding by maintaining the correctgrinding pressure between each pair of rolls. While this method ofsetting might prove somewhat helpful, it has the disadvantages of beingdifiicult to obtain accurate pressure readings, it does not take intoaccount the necessity for pressure variations with changing loadconditions, and it does not take into account the constantly changingcharacter of the roll surfaces which must be reground or sharpened atintervals. Because it does not take these elements into consideration,it wastes power and produces unnecessary wear on the machinery andexcessive maintenance requirements.

Flour is necessarily produced by a long series of gradual reductionsfrom the whole Wheat kernel. Each pair of rolls has an optimum pressurefor a given volume and type of stock for a particular milling operation.High quality uniform products require consistently accurate grindingwith a consistent degree of reduction performed at each step in theoperation. Individuals, no matter how skilled, have proved incapable ofmaintaining high quality uniform production. A more scientific,reproduceable method of setting roller mills has long been urgentlyneeded.

At each step in the milling process a certain definite extraction isdesired. This is most easily and conveniently expressed in terms of apercentage of flour which can be sieved through a certain sized cloth(for example, llXX) in a given length of time after the wheat stock haspassed through the roller mill. Depending upon which step in thereduction or milling process is involved, the desired extraction mayvary from 2-3 to 50 per cent. Generally speaking, the harder or closerthe grinding, the greater the extraction, although there comes a pointbeyond which the harder grinding only causes damage to the cellstructure and quality of the flour. When this occurs, the extractionrate actually drops due to a flattening of the stock. In each reductionoperation, there is a desired point where good extraction is obtainedwithout excessive damage to the flour cell structure and it is the goalof every miller to consistently operate his milling rolls at that point.

The friction and pressure of grinding brings about an increase of thetemperature of the stock being ground. I have found that the measurementand recording of this temperature increase in each milling operation isthe simplest, most accurate and beneficial indicia for controlling themilling reduction process. I have found that certain temperatureincreases during a particular milling operation give reliableindications of the extraction possible thereafter and reflect not onlythe pressure used, but also take into account the condition of the rolland the amount of feed to the roll. I have found that each pair of rollsin a particular milling operation has an optimum pressure andconsequently an optimum temperature increase. The lesser the variationin temperature increment of the stock from this optimum temperatureincrease, the greater the percentage of extraction will be. Byregulating the pressure to keep the increment as close as possible tothe optimum temperature increase I have found that a highly uniformquality product can be obtained.

It is possible and even probable for temperature increases on variouspairs of rolls in a mill to range from 2 or 3 degrees Fahrenheit to asmuch as 40 degrees Fahrenheit in extreme cases. Because of itsparticular condition one pair of rolls handling a similar load andidentical stock may produce temperature gains three times that of onepair of rolls supposedly doing the same work. Often times the same rollwill vary to a similar extent from day to day.

It is a general object of my invention to provide a novel and improvedmethod and apparatus for regulating the milling rolls in a flour millingoperation.

A more specific object is to provide novel and improved methods andapparatus for determining whether the pressure upon a given pair ofrolls during a particular milling operation should be increased ordecreased to accomplish the most eflicient milling operation.

A still more specific object is to provide a quick and ready means forthe miller in a particular milling operation to determine whenadjustments of the pressure upon a given set of rolls is needed and theextent of such needed adjustment.

Another object is to provide novel and improved methods and apparatusfor regulating the milling rolls in a flour milling operation which willtake into account pressure variations with changing load conditions andthe constantly changing character of the roll surfaces.

Another object is to provide novel and improved flour milling methodsand apparatus which will accomplish a substantial saving in power andwhich will eliminate unnecessary and wasteful wear and maintenancerequirements on the milling machinery.

Another object of my invention is to provide novel and improved methodsand apparatus for regulating flour milling rolls which will insuremaximum extraction and hence provide the most efiicient millingoperation and yields higher than were previously possible.

Another object is to provide flour milling methods and apparatus whichwill insure the production of uniform and high quality flour.

Another object is to provide novel methods and apparatus for regulatingflour milling rolls which will resuit in better air and temperatureconditions throughout the milling plant.

These and other objects and advantages of my invention will more fullyappear from the following description made in connection with theaccompanying drawings, wherein like reference characters refer tosimilar parts throughout the several views, and in which:

Fig. l is an end elevational view of one structural embodiment of myinvention; and

Fig. 2 is a somewhat diagrammatic perspective view of two pairs ofmilling rolls being operated in accordance with my invention.

One embodiment of my invention is illustrated in Figs. 1 and 2,including as in conventional milling a pair of power driven milling orgrinding rolls 5 and 6. These rolls 5 and 6 are mounted for rotationabout their longitudinal axis which, as shown, is disposed horizontally.Each of these rolls 5 and 6 is mounted at its end for rotation withinmounting brackets 7 and 8 which in turn are mounted upon a castingindicated generally as 9. The mounting bracket 7, as best shown in Fig.l, is rigidly ailixed to the casting 9 while the mounting bracket 8 ispivotally mounted thereupon as at 10.

The pivotally mounted mounting bracket 8 carries a mounting arm 11 whichhas an open ended housing 12 at its upper end. This housing has anopening 13 which accommodates a compression rod 14 which extendstransversely to the pair of rolls 5 and 6. This compression rod 14 has aloop 15 which pivotally connects it to a bracket 16 which in turn isrigidly affixed to the casting 9. As best shown in Fig. l, thecompression rod 14 is threaded at its other end as at 17 and carries inthreaded relation thereupon a compression plate 18. A coiled spring 19is also carried by the compression rod 14 between the compression plate18 and the interior walls of the housing 12.

An upstanding lug 20 on the mounting arm 11 carries a roll pressureadjustment wheel 21 in threaded relation, the inner end of the threadedmember 22 which carries this adjustment wheel being adapted to pivotfreely with respect to the end 17 of the compression rod 14.

Fig. 2 shows two pairs of such rolls disposed in their usual relativepositions. Mounted above these two pairs of rolls is an inverted -shapeddivider 24 which is comprised of a pair of angulated panels 25. Thecoarse unground material 26 is dropped from above upon the apex of thedivider 24 and slides downwardly along the divider panels 25 until itabuts against an adjustable feed gate 27, one of such gates beingprovided for each of the panels 25. These feed gates are adjustable toregulate the volume of the coarse unground material 26 which ispermitted to pass between the panel 25 and the feed gate itself. Thecoarse unground material, as clearly shown in Fig. 2, is permitted todrop downwardly between and into the bight of the rolls as they turn inthe directions shown.

Mounted upon each of the panels 25 in a central position as best shownin Fig. 2, and in the path of the descending coarse unground material26, is a thermometer bulb 28. This thermometer bulb is connected by acapillary tube 29 which in turn is connected to a thermometer dial ofthe conventional type 30. This type of temperature indicating apparatus28, 29 and 30 is wellknown in the art and it is therefore consideredunnecessary to go further into the details of construction thereof. Itis important, however, that the thermometer bulb 28 be positioned sothat the coarse unground material passes directly across and inregistering relation so that the temperature of such material will beaccurately indicated upon the thermometer dial 39 at all times.

A similar thermometer bulb 31 is mounted directly below the rolls 5 and6 at each of their ends and directly in the path of the ground stock asit passes from the bight of the rolls. This is best shown in Fig. Thethermometer bulb 31 is carried by a support arm 37 which in turn ismounted upon a rod 36 which is normally supported by the casting 9 andnormally carries a plurality of roll cleaning brushes (not shown). Apair of such thermometer bulbs 31 is mounted adjcent the opposite endsof each of such pair of rolls and in position so that the ground stockmust pass across the bulb. Each of such thermometer bulbs 31 has acapillary tube 32 associated therewith which connects the bulb to athermometer dial 33 which is carried on panel 34. Mounted above each ofthe thermometer bulbs 31 is a pair of shield members 35 which extend thelength of the bulb and are disposed between the bulb and one of therolls 5 and 6 as shown in Fig. 1.

In the utilization of my methods and apparatus the optimum temperatureincrease is determined for each pair of rolls for the particular millingoperation being performed by such rolls. I have found that by taking anextraction as often as about once a week and thereafter practicing myinvention in reliance upon the optimum temperature determined by suchextractions, that I can increase the efficiency of the mill and at thesame time produce a substantially more uniform product which is of highquality. To practice the invention the temperature of the stock bothbefore and after it passes between the rolls is determined by referenceto the dials 30 and 33. If the temperature increment as indicated byreference to these dials 30 and 33 is less than the optimum temperatureincrease as predetermined, the miller is immediately apprised of thefact that pressure upon the rolls should be adjusted by means of theadjustment wheel 21. Within a few minutes he can adjust the pressure bymeans of the adjustment wheel 21 so that the optimum temperatureincrement is attained. Of course, if the temperature increment asdetermined by reference to the dials is greater than the predeterminedoptimum temperature increase, then the pressure is decreased throughadjustment of the adjustment wheel 21 until the temperature increment isequal to the optimum temperature increase. I have found that thepressure upon each pair of rolls can be adjusted in this manner so thatthe temperature increment remains within about plus or minus one degreeFahrenheit from the optimum temperature increase.

One good example of the predetermination of the optimum temperatureincrease can be cited in connection with a stream of wheat materialwhich I call 1 Middlings Coarse. On this particular milling stream, Ifind a temperature increase during the process of grinding of 18 degreesFahrenheit produces optimum results. With this temperature increase Iobtain an extraction rate of 21 per cent through a mesh per lineal inchstainless steel wire cloth. In this particular operation there is 1.41pounds per minute per lineal inch of grinding surface.

Another example would be a stream which I term 6 Middlings whichrequires for optimum results a temperature increase of 12 degreesFahrenheit. Such a temperature increase provides a 30 per centextraction through a similar stainless steel wire cloth and .38 poundper minute per lineal inch of grinding surface.

One advantage of practicing my invention is that each pair of rolls canbe checked and adjusted by one man a number of times each day. Undermethods previously known such frequent adjustments were an impossibilitywithout employing a prohibitive number of men to accomplish the same.Even if such a large number of men were employed, varying loadconditions between the successive taking of the optimum temperatureincrease and the associated adjustments would destroy much of the valueof the adjustments. My invention immediately discloses the etfects andthe presence of such changing conditions so that necessary adjustmentswill be made at'once.

As a result of the use of this new method of regulating the pressure ofmilling rolls, I have found that the flour which is produced not onlyhas been definitely improved but I have been able to distribute theloads more evenly and to hold temperature increases to quite uniformlevels far below the former averages. This reduction in friction andgrinding pressures has incidently reduced the power required forgrinding by at least 25 per cent. Consequently, this method or systemalso saves on wear and required maintenance on the milling machinery. Italso results in better air and temperature conditions throughout theplant. This method goes a long way toward substituting scientificaccurate control for the old invention personal control commonly used. Ihave not yet been able to determine accurately the extent to whichbetter yields are obtained. However, it has already appeared obviousthat this method does produce better yields from a given millingprocess. In other words, I find that I can make a higher percentage offiour from any given quantity of wheat than was previously possible whenusing the old means.

Thus it can be seen that I have provided a novel method which requiresonly simple and cheap apparatus for regulating the milling rolls in aflour milling operation to obtain a uniform high quality product. I haveprovided a means whereby the miller can be immediately apprised whenvarying conditions require adjustment of the milling rolls and theextent to which such adjustment should be made. If an adjustment whichis made is too severe, that fact will immediately be indicated by theincrement in temperature as recorded upon the dials 30 and 33.

It should be noted that my method of determining the time, nature andextent of adjustment required in the pressure regulating apparatus of apair of milling rolls takes into account pressure variations caused bychanging load conditions and at the same time the constantly changingcharacter of the roll surfaces. At the same time, it eifects asubstantial saving in power and eliminates unnecessary and wasteful wearand maintenance requirements on the milling machines in addition toproviding maximum extraction and higher yields.

It will, of course, be understood that various changes may be made inthe form, details, arrangement and proportions of the various partswithout departing from the scope of my invention.

What is claimed is:

1. In the art of flour milling, the method which involves grinding grainunder atmospheric conditions to continuously produce a maximum anduniform extraction of flour from the grain, consisting in providing aconfined source of the grain under atmospheric conditions, continuouslyrecording the temperature of the grain before grinding, grinding thegrain under atmospheric temperature conditions, continuously recordingthe temperature of the grain as it leaves the grinding zone, andregulating the grinding force applied to the grain according to thedifierence between the said recorded temperature of the unground grainand the ground grain, increasing said grinding force when the differencein temperature is less than a predetermined amount and decreasing thecompressive force when the diiference in temperature is greater tomaintain a substantially constant diiference in temperature.

2. In the art of flour milling, the method which involves grinding grainunder atmospheric conditions to continuously produce a maximum anduniform extraction of flour from the grain consisting in providing aconfined source of the grain under atmospheric conditions, frequentlyrecording the temperature of the grain before grinding, grinding thegrain under atmospheric temperature conditions, frequently recording thetemperature of the grain as it leaves the grinding zone, and regulatingthe grinding force applied to the grain according to the differencebetween the said recorded temperature of the unground grain and theground grain, increasing said grinding force when the difference intemperature is less than a predetermined amount and decreasing thecompressive force when the difference in temperature is greater thansuch predetermined amounts to maintain a substantially constantdifference in temperature.

3. In the art of flour milling, the method which involves grinding grainunder atmospheric conditions to continuously produce a maximum anduniform extraction of flour from the grain, consisting in providing aconfined source of the grain under atmospheric conditions, continuouslyrecording the temperature of the grain before grinding, grinding thegrain under atmospheric temperature conditions, continuously recordingthe temperature of the grain as it leaves the grinding zone, and varyingthe grinding force applied to the grain according to the differencebetween the said recorded temperature of the unground grain and theground grain taken at approximately the same time, increasing saidgrinding force when the difference in temperature is less than apredetermined amount and decreasing the compressive force when thedifference in temperature is greater than such predetermined amount tomaintain a substantially constant difference in temperature.

4. In the art of flour milling, the method which involves grinding grainunder atmospheric conditions to continuously produce a maximum anduniform extraction of flour from the grain, consisting in providing aconfined source of the grain under atmospheric conditions, frequentlyrecording the temperature of the grain before grinding, grinding thegrain under atmospheric temperature conditions, frequently recording thetemperature of the grain as it leaves the grinding zone, and varying thegrinding force applied to the grain according to the diiference betweenthe said recorded temperature of the unground grain and the ground graintaken at approximately the same time, increasing said grinding forcewhen the dilference in temperature is less than a predetermined amountand decreasing the compressive force when the difference in temperatureis greater than such predetermined amount to maintain a substantiallyconstant difference in temperature.

References Cited in the file of this patent UNITED STATES PATENTS571,226 Favrow Nov. 10, 1896 2,580,651 Boyd, Jr. Jan. 1, 1952 FOREIGNPATENTS 514,933 Great Britain Nov. 21, 1939 519,869 Great Britain Apr.9, 1940

